Waste-eating bacteria research explored as power source for Air Force systems

Published Nov. 8, 2006
By William J. Sharp
Air Force Office of Scientific Research Public Affairs

ARLINGTON, Va. -- The Air Force Office of Scientific Research here recently awarded a 5-year grant to the University of Southern California worth approximately $4.5 million to lead a study on bioengineered fuel cells.

Bioengineered fuel cells are bacteria capable of producing electrical energy simply through the process of consumption. Bacteria that serve as catalysts in the fuel cells can eat a variety of carbon-based wastes and materials such as glucose, lactose, and glycerol. In turn, the bioengineered fuel cells can convert food intake into electrical power.

Leading the USC effort is Dr. Ken Nealson, professor of geobiology, department of Earth sciences. Nealson said microbes and bacteria have a number of interesting properties that make them attractive for converting organic energy sources into electricity and he is excited about the research.

According to Maj. Jennifer S. Gresham, AFOSR program manager for biophysical mechanisms, the Air Force has long been interested in developments in compact power sources.

"Developments in these sources could enable certain systems, such as unmanned aerial vehicles, to operate for longer periods of time without the use of conventional engines and batteries," Major Gresham said. "The bio-based fuel cells that could result from the efforts of Doctor Nealson and his team may help solve some of the challenges faced by these systems, including infrared signature detection, excessive noise and weight, and slow battery recharge. We believe his research may allow air vehicles to one day refuel themselves from their surroundings."

Added Mr. Nealson, "If this research works, if we can manipulate these cells to be better at power production while, at the same time, increasing their waste reduction capacity, then we will have achieved something very important to the Air Force."

"Microbes can eat a wide variety of things," Mr. Nealson continued. "Potentially, that makes them very versatile in how they can be used."

Standard fuel cells, he said, typically consume only a single compound or element.

"Since bacteria can eat dozens of things, you could have a fuel cell capable of turning a variety of organic energy sources into electricity," Mr. Nealson explained.

Bacteria as catalysts for energy conversion offer other interesting qualities, too.

"In comparison to expensive platinum catalysts, bacteria are virtually free - one needs only to grow them up in the quantities needed," Mr. Nealson said. "And bacteria are self-repairing systems, too. If stressed, the colony simply reforms and fixes itself.

"The challenge is that no one has yet been able to get the systems to produce enough electrical current for the systems to be taken seriously," Mr. Nealson said. "We have very good evidence now, as do a number of other labs, that these organisms have great energy production potential. Our goal is to learn the mechanism by how they turn organic compounds into useful electrical energy so we can exploit this capability and get the bacteria to produce even greater volumes of energy."

Shewanella oneidensis and geobactor are the current systems under investigation because, Nealson said, researchers know a lot about these bacteria forms.

Like the human process of breathing in oxygen and exhaling carbon dioxide, Shewanella oneidensis has the ability to 'inhale' certain metals and compounds, which may be toxic to humans, and 'exhale' these metals in an altered, non-toxic state. Researchers believe Shewanella oneidensis and other closely related microbes have a number of potential uses, including environmental clean up, because they can grow under a wide variety of conditions. Additionally, the bacteria could be used almost anywhere and do not cause disease in humans or other organisms.

Mr. Nealson's research consists of a number of thrust areas. The microbiology thrust area involves identifying components of the fuel cells to better learn how the energy transfer occurs. The second thrust area involves understanding how the fuel cells might be better engineered to maximize their interactions with the microbes. Genetic improvement of the microbes is the goal of the third thrust area to increase power production. The fourth thrust area is an examination of the communities of organisms working together. In this effort, researchers are looking to identify communities that show the greatest power production potential.

"I believe it is within reach in the very near future to begin to understand the basic mechanisms involved in electricity generation," Mr. Nealson said. "We can then exploit this knowledge to increase the power production of the cells under study by many orders of magnitude. With time and a little luck, we may be able to increase power enough to accomplish a number of laudable goals, but only if we understand the mechanisms involved."

USC will collaborate on the multidiscipline university research initiative - or MURI - with Rice University in Houston.